Everything runs in dinars, from deposit to payout, so there is no conversion between your bank and your balance. The methods split three ways: instant bank transfers and cards, vouchers and counter-paid cash, and the betting shops themselves.
They differ not in what arrives, but in what they ask of you. The bank route depends on your bank letting that kind of transaction through, a voucher asks for no card at all, and the counter asks only for the walk to a payment point.
The differences show on the withdrawal side, and one step decides the rest: proving who you are. A licensed operator in Serbia is legally required to verify a player before paying out, so it costs a few minutes on day one and a weekend if it waits until a payout is due.